Method for manufacturing dies  formed with a dielectric layer

ABSTRACT

A method of manufacturing dies formed with a dielectric layer is revealed. A liquid dielectric layer is formed on the dicing tape. The liquid dielectric layer is heated to be sticky. Then, a wafer is attached to the dielectric layer on the dicing tape. The wafer is diced into a plurality of dies on the dicing tape. The dies with attached portions of the dielectric layer are picked up to be peeled and separated from the dicing tape. The implementation of the dicing tape can be expanded to resolve various issues such as wafer contaminations, wafer warpage due to multiple heating and mismatching of thermal expansion coefficients, and wafer singulating problems due to alignment difficulties. The wafer handling steps can further be reduced to increase processing yield and to enhance easy and better processing.

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing semiconductordevices by wafer dicing, and more particularly to a method ofmanufacturing dies formed with a dielectric layer.

BACKGROUND OF THE INVENTION

In semiconductor industries, the manufacture of semiconductor devicesprimary divides into three stages: wafer fabrication, chip formation,and chip assembly. During wafer fabrication and chip formationprocesses, a dielectric layer is directly formed on a wafer for dieattachment or for wafer-level packaging where the dielectric layer canbe B-stage films, solid films or epoxy liquid pastes, however, solidfilms are more expensive. Therefore, it is more common to dispose liquidpastes on a wafer such as stencil printing on the back surface of awafer but the wafer is easily contaminated.

FIG. 1 is the block diagram of a conventional process flow formanufacturing dies with a dielectric layer. Step 1 is to provide awafer. Step 2 is to attach a protecting tape to the active surface ofthe wafer to avoid contamination of liquid dielectric materials on theactive surface in sequent steps. Step 3 is to turn the wafer upside downwith the back surface facing upward. Step 4 is to form a dielectriclayer on the back surface of the wafer by stencil printing or any knownliquid disposition methods where the cover area of the dielectric layershould be smaller than the one of the back surface of the wafer to avoidliquid bleeding to the sides of the wafer or even to the protectingtape. Step 5 is to thermally cure the dielectric layer on the wafer toreach certain degree of dryness and curing to avoid serious bleeding inStep 6. In step 5, since the dielectric layer is thermally cured,dimension shrinkage due to curing is unavoidable. Moreover, the wafer isalso under heating at the same time, there is a thermal mismatchingissue due to different thermal expansion coefficients and dimensionsbetween the wafer and the dielectric layer. Then, step 6 is to turn theback surface of the wafer downward to attach to a dicing tape so thatthe dielectric layer is attached to the dicing tape by the adhesion ofthe dicing tape. Afterward, step 7 is to remove the protecting tape toexpose the active surface of the wafer. Then, step 8 is to dice thewafer into a plurality of individual dies. Finally, step 9 is to pick upthe dies from the dicing tape. Therefore, the wafer with the dielectriclayer will experience multiple heating steps leading to serious waferwarpage issues due to mismatching of thermal expansion coefficients anddimensions, more the worse, the curing shrinkage of dielectric layercausing wafer handling difficulties in the following processes.Furthermore, since the wafer has to go through multiple turning steps,the risk of lower yields and higher cost is relatively increased. Oncethe back surface of the wafer is not turned upside down in step 6 andthe protecting tape is not removed to expose the active surface in step7, singulation in step 8 has to be done from the back surface of a waferwhere scribe line alignment for wafer dicing processes becomesdifficult.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a method ofmanufacturing dies formed with a dielectric layer to resolvecontamination of dielectric layer on the active surface of a wafer aswell as the wafer warpage due to multiple heating steps exerted on awafer during formation of dielectric layer and mismatching of thermalexpansion coefficients and dimensions. Moreover, the wafer turning stepsare decreased to achieve higher yields with lower cost.

The second purpose of the present invention is to provide a method ofmanufacturing dies formed with a dielectric layer is to resolve waferdamages due to turning wafers for wafer dicing processes as well asalignment issues due to wafer dicing from the back surface of a waferleading to easy and better processing.

According to the present invention, a method of manufacturing diesformed with a dielectric layer is revealed, primarily comprising thefollowing steps: Firstly, a dicing tape is provided. A liquid dielectriclayer is formed on the dicing tape. The liquid dielectric layer isheated to be sticky, i.e., in B-staged or partially cured state. A waferis attached to the dielectric layer on the dicing tape. The wafer andthe dielectric layer are diced to form a plurality of dies each having acertain portion of the dielectric layer attached. The dies are picked upwith the corresponding attached portions of the dielectric layer arepeeled and separated from the dicing tape.

The method of manufacturing dies formed with a dielectric layeraccording to the present invention has the following advantages andfunctions:

-   1. Through the sequence of processing steps by preforming the    dielectric layer on the dicing tape then the wafer is attached as a    technical means, dicing tape can commonly implement in formation of    dielectric layer as well as in wafer dicing step to resolve the    contamination of dielectric layer on the active surface of the wafer    as well as the wafer warpage due to multiple heating steps exerted    on the wafer during formation of dielectric layer and mismatching of    thermal expansion coefficients and dimensions. Moreover, the wafer    turnover time is also decreased to achieve higher yields with lower    cost.-   2. Through the sequence of processing steps by performing the    dielectric layer on the dicing tape then the wafer is attached as a    technical means, dicing tape can commonly implement in formation    step of dielectric layer as well as in wafer dicing step to expose    the active surface of the wafer to resolve wafer damages due to    turning wafers for wafer dicing processes as well as alignment    issues due to wafer diced from the back surface of a wafer leading    to easy and better processing.-   3. Through the assembly of a spin-coating stage and positioning ring    and the sequence of processing steps as a technical means, the    excess bleeding of dielectric layer can be accommodated by the    annular groove on the spin-coating stage to avoid bleeding    contamination of dielectric layer to the attaching area of    positioning ring.-   4. Through the dielectric layer having the characteristic of    multiple-curing stages and transferred from the dicing tape to the    wafer as a technical means, the preformed dielectric layer can    replace the conventional adhesive film as die-attaching paste or    encapsulant for wafer level packaging to reduce the cost.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow block diagram for a conventional method ofmanufacturing dies formed with a dielectric layer.

FIG. 2 is a process flow block diagram for a method of manufacturingdies formed with a dielectric layer according to the first embodiment ofthe present invention.

FIGS. 3A to 3G are the cross-sectional views of components in processingsteps during the method according to the first embodiment of the presentinvention.

FIGS. 4A to 4G are the three-dimensional views and cross-sectional viewsof components in the processing steps during the method according to thesecond embodiment of the present invention.

FIGS. 5A to 5C are enlarged cross-sectional views of components from theformation step of the dielectric layer to the wafer attaching stepduring the method according to the second embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the attached drawings, the present invention isdescribed by means of the embodiment(s) below where the attacheddrawings are simplified for illustration purposes only to illustrate thestructures or methods of the present invention by describing therelationships between the components and assembly in the presentinvention. Therefore, the components shown in the figures are notexpressed with the actual numbers, actual shapes, actual dimensions, norwith the actual ratio. Some of the dimensions or dimension ratios havebeen enlarged or simplified to provide a better illustration. The actualnumbers, actual shapes, or actual dimension ratios can be selectivelydesigned and disposed and the detail component layouts may be morecomplicated.

According to the first embodiment of the present invention, a method ofmanufacturing dies formed with a dielectric layer is illustrated in FIG.2 for process flow block diagram and FIGS. 3A to 3G for thecross-sectional views of components in processing steps during themethod. The method of manufacturing dies formed with a dielectric layerprimarily comprises the steps as shown in FIG. 2 where the detaildescription of each step is described as follows.

Firstly, step 11 is performed to provide a dicing tape 110, as shown inFIG. 3A. The dicing tape 110 can be a UV blue tape or otherphotosensitive adhesive tapes to firmly hold the dies during wafersingulation processes without separation where the adhesion of thedicing tape 100 can be reduced or eliminated by radiating UV light inthe following processes. The dicing tape 110 is attached to a stage 140in order to keep the dielectric layer 120 horizontal (as shown in FIG.3C). The stage 140 can be a hot plate to heat the dielectric layer 120during wafer attaching step which will be explained in detail in step14. Preferably, a positioning ring 170 is attached to the peripheries ofthe dicing tape 110 to support the dicing tape 110 in step 11 so thatthe wafer 130 is not damaged nor deformed during processing. Normally,the positioning ring 170 can be made of metal such as stainless steel,aluminum, iron, etc. having an opening larger than the attached wafer130 (as shown in FIG. 3E).

Then, step 12 is performed to form a liquid dielectric layer 120 on thedicing tape 110, as shown in FIG. 3C, where the dielectric layer 120 hasthe characteristic of multiple-curing stages. In the present embodiment,the dielectric layer 120 can be formed on the dicing tape 110 by stencilprinting. For example, a stencil 150 is placed on top of the dicing tape110 as shown in FIG. 3A, and then a scraper 160 scraps a liquiddielectric material 121 into the stencil 150 as shown in FIG. 3B. Afterremoving the stencil 150 and the scraper 160, the dielectric layer 120transformed from the liquid dielectric material 121 is formed on thedicing tape 110 as shown in FIG. 3C. The liquid dielectric layer 120 isformed in a printed pattern not smaller than the attaching area of thewafer 130 (as shown in FIG. 3E) to allow larger alignment tolerance foreasy wafer attachment to enhance the processing steps.

Next, step 13 is performed to heat the liquid dielectric layer 120 to besticky as shown in FIG. 3C again. In the present embodiment, the liquiddielectric layer 120 is heated by the hot plate 140 where the dielectriclayer 120 becomes B-staged or in partially cured state. Therefore, aconventional wafer heating step is eliminated, moreover, the shrinkageof the dielectric layer 120 due to curing will have no effect on thewafer 130.

Next, step 14 is performed to attach a wafer 130 to the dielectric layer120 on the dicing tape 110 as shown in FIGS. 3D and 3E. Therein, thewafer 130 is attached to the dielectric layer 120 by heating thedielectric layer 120 and pressing the wafer 130. In the presentembodiment, the attaching surface of the wafer 130 adhered by thedielectric layer 120 can be the back surface 132 to make the dielectriclayer 120 as a die-attaching adhesive. Even the dielectric layer 120 isbleeding, the active surface 133 of the wafer 130 will not becontaminated to resolve the conventional formation of dielectric layerby multiple heating steps leading to wafer warpage issues and tosimplify wafer turnover time to meet the requirements of higher yieldswith lower cost. In another embodiment, the attaching surface of thewafer 130 for attaching the dielectric layer 120 can be the activesurface 133 to make the dielectric layer 120 as a wafer-level packaginglayer.

Next, step 15 is performed to dice the wafer 130 and the dielectriclayer 120 as shown in FIG. 3F. A blade 180 cuts through the wafer 130and the dielectric layer 120 to form a plurality of individual dies 131(as shown in FIG. 3G). Each die 131 has a certain portion 122 ofdielectric layer 120 attached, i.e., the cutting depth of the blade 180exceeds the thickness of the wafer 130 and the dielectric layer 120without cutting through the dicing tape 110. Preferably, after step 15,the adhesion of the dicing tape 110 to the diced dielectric layer 120can be reduced or eliminated by radiating UV light.

Next, step 16 is performed to pick up the dies 131 as shown in FIG. 3GSince the dielectric layer 120 is also diced in step 15, each die 131 isattached with a certain portion 122 of the dielectric layer 120. In step16, the attached portions 122 of the dielectric layer 120 are peeled andseparated from the dicing tape 110 when the dies 131 are picked up by asucker 190. Furthermore, preferably, the dielectric layer 120 has thecharacteristic of multiple-curing stages so that the dielectric layer120 is still adhesive after picking up the dies 131 to be adie-attaching adhesive for die attachment where the dielectric layer 120can replace the conventional die-attaching film without extradispensing, printing, or placing die-attaching materials to be low-costdie-attaching materials.

According to the second embodiment of the present invention, anothermethod of manufacturing dies formed with a dielectric layer isillustrated from FIG. 4A to FIG. 4G for the three-dimensional views andcross-sectional views of components in the processing steps and fromFIGS. 5A to 5C for enlarged cross-sectional views of components from theformation step of the dielectric layer to the wafer attaching step. Thecomponents used in the method of manufacturing dies with dielectriclayer according to the present embodiment are almost the same as theones in the first embodiment, therefore, the same component numbers areused.

As shown in FIG. 4A, firstly in step 11, a dicing tape 110 is providedwhere the dicing tape 110 can be a UV blue tape. The dicing tape 110 isplaced on a spin-coating stage 240 for keeping the dielectric layer 120horizontal (as shown in FIG. 5B) in step 12. The spin-coating stage 240can be a hot plate to heat the dielectric layer 120 to remove solventinside in step 13 and to become more adhesive during attaching the wafer130 (as shown in FIG. 5C) in step 14. Preferably, as shown in FIGS. 5Ato 5C, the spin-coating stage 240 has an annular groove 241 so that theportions of the dicing tape 110 located on the annular groove 241concavely deform when the dicing tape 110 is fixed by a suction forcefrom the spin-coating stage 240.

As shown in FIG. 4D, a liquid dielectric layer 120 is formed on thedicing tape 110 where the liquid dielectric layer 120 has thecharacteristic of multiple-curing stages. In the present embodiment, thedielectric layer 120 can be disposed on the dicing tape 110 by spincoating where the actual operations are shown in FIGS. 4B and 4C. Dropsof liquid dielectric material 121 are disposed at the center of thedicing tape 110 on the spin-coating stage 240. Simultaneously, thespin-coating stage 240 spins to spread the liquid dielectric material121 as shown in FIG. 4C and further to form the liquid dielectric layer120 as shown in FIG. 4D. As shown in FIG. 5A, when the excess liquiddielectric material 121 is dispensed which will bleed out during spincoating, the excess liquid dielectric material 121 may be accommodatedin deformed portions of the dicing tape 110 on the annular groove 241 toavoid contaminations of the excess liquid dielectric material 121bleeding to the peripheral area during spin coating. Then, thedielectric layer 120 is heated to be sticky, such as in B-staged or inpartially cured state, as shown in FIG. 5B and FIG. 4D.

In the present embodiment, as shown in FIG. 4D and FIG. 5B, apositioning ring 170 is attached to the peripheries of the dicing tape110 after the dropping sub-step mentioned above. Preferably, thepositioning ring 170 is not in direct contact with the dielectric layer120 by accommodation of the annular groove 241. Then, as shown in FIG.4D and FIG. 5C, a wafer 130 is attached to the dielectric layer 120 onthe dicing tape 110 by pressing to make the wafer 130 closely andsmoothly attach to the dielectric layer 120 and the bleeding of thedielectric layer 120 can be accommodated by the annular groove 241, asshown in FIG. 5C. During attaching the wafer 130, the dielectric layer120 is heated to be adhesive. As shown in FIG. 4E, the positioning ring170 carrying with the dicing tape 110, the dielectric layer 120 and thewafer 130 can easily be released from the stage 240.

As shown in FIG. 4F, a blade 180 dices the wafer 130 and the dielectriclayer 120 alone the scribe lines to form a plurality of individual dies131 (as shown in FIG. 4G). Each die 131 has certain portions 122 of thedielectric layer 120 attached (as shown in FIG. 4G). Therein, theattached surface of the wafer 130 by the dielectric layer 120 is a backsurface 132 with an exposed active surface 133 facing upward. Then, thedicing tape 110 is radiated with UV light to reduce or eliminate theadhesion for easily picking up dies in the following processes. As shownin FIG. 4G, the dies 131 are picked up by a sucker 190 where thecorresponding attached portions 122 diced from the dielectric layer 120are peeled and separated from the dicing tape 110.

Therefore, according to the present invention of manufacturing diesformed with a dielectric layer, the dicing tape 110 can commonly beimplemented in formation of dielectric layer 120 and in wafer dicingprocesses. One of the most specific functions is that when thedielectric layer 120 is formed and attached to the wafer 130, the activesurface 133 of the wafer 130 is exposed facing upward to resolve waferdamages due to turning wafers for conventional wafer dicing processes aswell as alignment issues due to wafer dicing from the back surface of awafer to enhance easy processing.

The above description of embodiments of this invention is intended to beillustrative but not limited. Other embodiments of this invention willbe obvious to those skilled in the art in view of the above disclosurewhich still will be covered by and within the scope of the presentinvention even with any modifications, equivalent variations, andadaptations.

1. A method of manufacturing dies formed with a dielectric layer,comprising the steps of: providing a dicing tape; forming a liquiddielectric layer on the dicing tape; heating the liquid dielectric layerto be sticky; attaching a wafer to the dielectric layer on the dicingtape; dicing the wafer and the dielectric layer to form a plurality ofdies each having a certain portion of the dielectric layer attached; andpicking up the dies with the attached portions of the dielectric layerpeeled and separated from the dicing tape.
 2. The method as claimed inclaim 1, wherein the dicing tape is attached to a stage for keeping thedielectric layer horizontal during the providing step of the dicingtape.
 3. The method as claimed in claim 2, wherein the stage is a hotplate to heat the dielectric layer during the wafer attaching step. 4.The method as claimed in claim 3, wherein the dielectric layer is in apartially cured state by the heating stage during the heating step ofthe liquid dielectric layer.
 5. The method as claimed in claim 1,wherein the dielectric layer is formed by stencil printing during theforming step of the liquid dielectric layer.
 6. The method as claimed inclaim 5, wherein the forming step of the liquid dielectric layerincludes the sub-steps of: placing a stencil on the dicing tape; andscraping a liquid dielectric material into the stencil by using ascraper to form the dielectric layer on the dicing tape.
 7. The methodas claimed in claim 5, wherein the dielectric layer is formed in aprinted pattern not smaller than the attaching area of the wafer.
 8. Themethod as claimed in claim 1, wherein a positioning ring is attached tothe peripheries of the dicing tape during the providing step of thedicing tape.
 9. The method as claimed in claim 1, wherein the dielectriclayer is formed on the dicing tape by spin-coating during the formingstep of the liquid dielectric layer.
 10. The method as claimed in claim9, wherein the forming step of the liquid dielectric layer includes thesub-steps of: placing the dicing tape on a spin-coating stage; anddropping the liquid dielectric material on the dicing tape on thespin-coating stage and simultaneously spinning the spin-coating stage.11. The method as claimed in claim 10, wherein the forming step of theliquid dielectric layer further includes the sub-step of attaching apositioning ring to the peripheries of the dicing tape after thedropping sub-step.
 12. The method as claimed in claim 11, wherein thespin-coating stage has an annular groove located outside the wafer butinside the positioning ring.
 13. The method as claimed in claim 1,wherein the dielectric layer has the characteristic of multiple-curingstages and the dielectric layer is still adhesive after the picking upstep.
 14. The method as claimed in claim 1, wherein the dicing tape is aUV blue tape.
 15. The method as claimed in claim 1, further comprisingthe step of reducing the adhesion of the dicing tape after the dicingstep and before the picking up step.
 16. The method as claimed in claim1, wherein the attached surface of the wafer coated with the dielectriclayer is a back surface.
 17. The method as claimed in claim 1, whereinthe attached surface of the wafer coated the dielectric layer is anactive surface.